promise-stream.js

/**
 * Convert a promise to a stream instance.
 *
 * @author Allex Wang ([email protected])
 *
 * MIT Licensed
 *
 * GistID: 03949e7ce81b740adba9fd31aff9b7c2
 * GistURL: https://gist.github.com/03949e7ce81b740adba9fd31aff9b7c2
 */
'use strict';

var Readable = require('stream').Readable;

class Streamify extends Readable {

  constructor(promise, options) {
    super(options);

    this.__promise = promise;
    this.__resolvingPromise = false;
  }

  _read() {
    var self = this;
    if (!self.__resolvingPromise) {
      self.__resolvingPromise = true;
      self.__promise.then(
        value => {
          if (value && typeof value !== 'string') {
            value = typeof value === 'object' ? JSON.stringify(value) : value.toString();
          }
          self.push(value);
          self.push(null);
        },
        error => {
          self.emit('error', error);
          self.push(null);
        }
      );
    }
  };

}

module.exports = (promise, options) => new Streamify(promise, options)